A common type of helicopter is provided with a main rotor and a tail rotor. The main rotor supplies the primary forces for flight of the helicopter and the tail rotor provides stability and influence on the flight direction of the helicopter. The tail rotor of the helicopter is sensitive for wind disturbances which affects the manoeuvrability of the helicopter. These wind disturbances also creates undesirable vibrations which may be transmitted to the fuselage of the helicopter. Also, oscillations of the tail rotor blades are a primary source of undesirable vibrations. Such oscillations may occur from the so-called “scissors mode” motions of the rotor blades in relation to each others. In this mode the blades oscillates relative to the drive shaft and to each others in the plane of rotation of the rotor blades. The oscillations and vibrations generated by the tail rotor are undesirable because they increase the mechanical stress of the components in the helicopter.
Document U.S. Pat. No. 3,999,887 discloses a connecting assembly for the tail rotor of a helicopter. The assembly is provided with flexible straps which interconnect the rotor blades with the connecting assembly. The connecting assembly is also provided with layers of a viscoelastic material which are disposed normal to the axis of rotation of the drive shaft. By proper selection of the viscoelastic material for the layers oscillations and vibrations can be reduced through the damping characteristics of the viscoelastic material. The layers of viscoelastic material are bound to support or cover plates in the connecting assembly. Bolts and nuts lock the cover plates in a fixed position relative to the drive shaft.
The objective problem to be solved by the present invention is to increase the manoeuvrability of a helicopter.
Another objective problem to be solved by the present invention is to achieve a rotor damper which effectively dampens oscillations and vibrations of a tail rotor of a helicopter.
A further objective problem to be solved by the present invention is to achieve a rotor damper which is easy to replace and which can be replaced in a short period of time.
A still further objective problem to be solved by the present invention is to easy and in a short period of time change the damping characteristics of a rotor damper.
A still further objective problem to be solved by the present invention is to achieve a rotor damper for a tail rotor, which is adapted to an unattended helicopter.